1 List of United States cities by population. ^ 2  Population projection is that of the entity known since 2016 as Ciudad de MÃ©xico and previously as the Distrito Federal. ^  Population estimate is that of the Toronto census division, which consists solely of the City of Toronto.
Lens (optics) For other uses, see Lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
noun. The lens in these glasses are blue. The lens in these glasses are blue. The definition of a lens is a piece of glass or other hard clear material molded with one side flat and the other curved or both sides curved that forms an image by bringing together or spreading the light that passes through it.1  An example of lens is the clear pieces covering the eyes in eye glasses.ens-Computer Definition. The glass or plastic elements that focus light onto analog film or a digital sensor in a still or video camera. Lens quality is just as important in digital cameras as it was in the Daguerreotype cameras in the 1800s.